The main goal of this project is to define immunological mechanisms in the Syrian hamster with particular emphasis on the role of various Ig classes. Experiments are devised to determine why only one Ig class may be preferentially stimulated depending upon antigenic presentation, what are the relative protective roles (phagocytosis promoting, tumor suppression or enhancement, etc.) of each Ig class and how can the immune response be channeled for synthesis in one or another Ig class.